In the Standard document for IS-2000-2, “Physical Layer Standard for cdma2000 Spread Spectrum Systems”, release 0, July 1999, the base station is allowed to selectively disable transmission on certain forward channels on a frame by frame basis. This is referred to as discontinuous transmission, or DTX. However, information as to whether a particular frame has been transmitted or has not been transmitted is unknown to the mobile station. In the above-referenced Standard the following channels are defined as having DTX capability: Forward Dedicated Control Channel (F-DCCH), Forward Supplemental Channel 1 (F-SCH1) and the Forward Supplemental Channel 2 (F-SCH2), the latter two channels being collectively referred to herein as F-SCHn.
There are several algorithms that are executed by the mobile station that require information as to whether a frame was actually transmitted. This is referred to herein generally as a “DTX detection problem”. Three examples of such algorithms are now discussed.
A first algorithm pertains to whether forward link power control is enabled on the F-DCCH or the F-SCHn. In this case the outer power control loop operates to update the current set point or operating point based on the frame error information, provided by the cyclic redundancy check (CRC) calculation. If a frame was not transmitted, then the mobile station should not update the current outer power control loop set point. In order to accomplish this the mobile station should have some capability to detect whether an actual frame transmission has occurred, or has not occurred.
A later Standard, IS-2000-2, “Physical Layer Standard for cdma2000 Spread Spectrum Systems”, release A, Jun. 9, 2000, specifies a forward link power control mode on the F-DCCH (Quality Indicator Bit (QIB) power control). The algorithm also requires detection of the F-DCCH frame transmission.
The IS-2000-2, “Physical Layer Standard for cdma2000 Spread Spectrum Systems”, release A, Jun. 9, 2000 Standard also allows a power control subchannel on the forward link to be transmitted on the Forward Fundamental Channel (F-FCH) or on the F-DCCH based on a parameter FPC_PRI_CHAN. When the power control subchannel is transmitted on the F-DCCH, a mobile station supervision procedure algorithm requires DTX detection.
As should be appreciated, it is important that the mobile station operating under the above-described conditions be capable of determining whether DTX was in effect on a frame-by-frame basis in order to ensure proper functionality. Prior to this invention this important need was not satisfied, and the DTX detection problem was not resolved.